1. Field
The present disclosure relates to a washing machine. More particularly, the present disclosure relates to arrangement of a clutch unit and a cam switch of a washing machine that can selectively transmit power to a washing shaft and a dewatering shaft, and a control method of the washing machine.
2. Description of the Related Art
A washing machine is a machine for washing clothing using electric power, and is largely classified into a drum washing machine and an automatic washing machine.
Generally, the automatic washing machine includes a washing tub for receiving washing water, a dewatering tub rotatably disposed inside the washing tub, a pulsator rotatably disposed on the bottom of the dewatering tub, a driving device for rotating the dewatering tub and the pulsator, and a clutch unit for selectively transmitting power to the dewatering tub.
When the dewatering tub and the pulsator rotate while laundry and detergent water are introduced into the dewatering tub, the pulsator stirs the laundry introduced into the dewatering tub together with the washing water to remove the impurities from the laundry.
The pulsator is directly connected to the driving device and is always rotated when the driving device is operated. However, the dewatering tub is selectively rotated by the clutch unit connected to a dewatering shaft. Therefore, when a washing mode is performed, the rotation of the dewatering shaft is prevented by the clutch unit so that only the pulsator is rotated, and when a dewatering mode is performed, the dewatering shaft is rotated by the clutch unit so that the dewatering tub is rotated together with the pulsator.
In general, the clutch unit is configured such that the dewatering shaft is rotated or prevented from rotating through a coupling that is vertically moved by a clutch motor.
A configuration for switching between the washing mode and the dewatering mode using the clutch motor is disclosed in Korean Patent Publication No. 10-2004-0046064 (title of invention: method of switching power transmission mode of washing machine, publication date: 2004 Jun. 5).
The conventional washing machine for switching between the washing mode and the dewatering mode uses a method of stopping the clutch motor after driving the clutch motor for a predetermined time when a contact signal of the clutch motor is detected. At this time, the predetermined time is determined by calculating the time required for rotating a cam rotated by the clutch motor by a predetermined angle in consideration of the rotational speed of the clutch motor under the rated voltage and frequency conditions. On the other hand, the predetermined time may be measured by a method of measuring the time using an internal clock or a method of measuring the number of pulses of electricity flowing through the contact point.
However, the rotational speed of the clutch motor when the rated voltage and frequency are not applied to the washing machine is different from the rotational speed of the clutch motor when the rated voltage and frequency are applied. Accordingly, when the rated voltage and frequency are not applied to the washing machine, the stop position of the cam is different from the design stop position even if the clutch motor stops after the predetermined time.
Further, in the method of measuring the number of pulses, when the rated voltage and frequency are not applied to the washing machine, the number of pulses varies accordingly. Therefore, when the clutch motor stops after the predetermined time, the cam may stop at the design stop position. However, in a region where the power supply environment is poor, a noise component may occur in the power supply frequency. In this case, an error occurs in the number of pulses measured so that the stop position of the cam becomes different from the design stop position.
When the cam rotated by the clutch motor does not come to the design stop position, the coupling change of the clutch unit is incomplete so that the coupling may be damaged.